Elastic yarn



Patented Jan. 23., 1951 ELASTIC YARN Bontwell 1!. Foster, Maplewood, N. 1., assignmto United States Rubber Company, New York, N. Y., a corporation of New Jersey Application November 18, 1948, Serial No. 60,647

3 Claims. I

This invention relates to elastic yarn compris-' ing a rubber core thread having a coating formed of an extensible resinous film such as nylon.

It has been proposed heretofore to provide a rubber thread with an inelastic cover such as a coating of paste applied thereto to hold the rubber thread stretched and non-elastic until it is woven or knitted into a fabric. It has also been proposed heretofore to provide a rubber thread having a coating of thermoplastic adhesive secured thereto for the purpose of bonding a textile cover to the rubber thread.

The present invention relates to an elastic yarn in/which the stretched rubber core thread is not provided with a textile cover as heretofore, but in place thereof is provided with an elastic nontacky resinous coating of film-forming material, of uniform thickness, that protects the rubber thread and is capable of stretching and retracting therewith. Such cc ating is preferably formed of nylon applied as a solution directly to the bare, stretched rubber thread.

One object of the present invention is to provide a rubber core thread having a tough, durable coating in the form of a continuous, elastic protecting film that is capable of holding the rubber core stretched an appreciable amount in the relaxed composite strand or elastic yarn. Another object is to provide an elastic yarn of this type which is capable of stretching with the rubber core from to several hundred per-cent as desired.

This stretchable covering film is well adapted to protect the core from the oxidi-ing action of the air and frcm the deteriorat ng action of perspiration, and from oil, dirt and grease, as well as from washing and cleaning fluids to which the 'elastic yarn may be subjected when embodied in wearing apparel. Another advantage of the construction of the present invention is due to its aid in the elimination of the characteristic odor of rubber that frequently accompanies wearing apparel constructed of ordinary elastic yarn. Still another advantage of the present invention is that the coating may be made extremely thin, with the result that an elastic yarn that is much finer than the textile covered elastic yarns available heretofore can be produced, in that the elastic yarn of the present invention may be made to have a length of 20,000 to 25,000 yards to the The elastic yarn contemplated by the presen invention preferably has a round rubber core pound thereof in the relaxed condition.

directly applied thereto a continuous coatin of stretchable resinous material. The material used is preferably the highly elast c, film-forming linear polyamide commonly called nylon. For 5 application to the core thread it is dissolved in a suitable solvent such as concentrated formic acid. This nylon solution is applied to the advancing rubber thread while the latter is held stretched to a selected degree of elongation. The tension is maintained until the nylon coating has solidified by evaporation of the solvent. In the dried condition the coating will hold the core stretched, say or more, in the finished elastic yarn.

The above and other features of the elastic yarn contemplated by the present invention, and a method of manufacturing the same, will be further. understood from the followin description when read in connection with the accompanying drawing, wherein,

Fig. 1 is a side view of an elastic yarn constructed in accordance with the present invention; and

Fig. 2 is a schematic side elevation of appa- 26 ratus for producing the elastic yarn of Fig. l.

The elastic yarn of the present invention, as shown in the drawing, comprises a round thread ID of vulcanized rubber having directly applied thereto a continuous nylon coatin II. This coating may be made much thinner than the fibrous textile covers commonly employed heretofore upon elastic yarns; for example, the weight of the coating I I may constitute only about of the weight of the e astic yarn with the rubber core "I constitut ng the remaining of the weight, although the relative weights of the coating and core may be varied extensively.

The coating H is applied to the rubber core in the form of a nylon solution which should be applied in such manner that the core is uniformly coated with a film of even thickness. This may be done by passing the thread through a bath of nylon solution, and drying the coated thread without allowing it to come in contact with any solid surface. The solution may be applied by means of a rotating applicator wheel, or the solution may be applied by other means.

The nylon selected should be one that is capable of being stretched a substantial amount at room temperatures, and preferably from one hundred to several hundred percent, when applied to the rubber core as a coating. The nylon naturally has suflicient strength to hold the rubber core thread stretched say 25% or more, so 55 that the core thread will always be under some tension in the finished, relaxed yarn. The elastic yarn when stretched is capable of retracting to substantially its original length, and although it may not recover instantaneously, the elastic recovery is sufliciently quick to meet the requirements of elastic wearing apparel so that the apparel will contract and stretch with the body movement of the wearer.

One form of apparatus which may be employed to make the elastic yarn of the present invention is shown in Fig. 2 of the drawing, wherein the bare vulcanized rubber thread I is supplied by a let-off spool I2. This spool preferably has the usual end flanges and pintles I3 which are slidably mounted in slots provided in the upper end portions of the upright posts I4. This supply spool I2 rests upon a power driven roller I which is journaled in the spaced posts I4 and is provided with the driving gear I6. The arrangement is such that the supply of rubber wound upon the spool I2 engages the driving surface of the roller I5 so that this spool will be rotated at the same surface speed as the roller I5, irrespective of the size of the rubber supply wound upon this spool. This insures delivery of the rubber thread II] from the spool I2 at a uniform speed to stretch the thread the desired amount.

This rubber thread I0 is shown as passing from the l't-off spool I2 about a free running grooved roller I1, and then downwardly in a vertical direction to the apparatus which applies the nylon coating II. This apparatus as shown comprises a coating tank I8 which is supported in a fixed position, and a constant-level device comprising a feed tank l9 which is supported for floating movement by means of a bale and coil supporting spring 2|, and a tube 22 connecting the two tanks. The arrangement is such that the supply receptacle l9 will move downwardly as the volume of liquid therein increases (when the tank is being filled), and will move upwardly as the supply of liquid is depleted by flowing into tank I8, to thereby maintain the level of the surface of the liquid in the receptacle I 9 and in tank I8 substantially constant. The tube 22 connecting the two receptacles does not interfere with the movement of the tank I9. Within the bottom of the fixed receptacle I8 is mounted a small glass tube 23, so that the stretched rubber thread I0 may pass downwardly through the coating solution within the tank I8 and then through this tube 23 which is only slightly larger than the rubber thread.

The receptacle I8 contains a linear polyamide which is dissolved in a suitable solvent such as formic acid; for example, a solution of nylon in 90% formic acid. This solution is prepared by ball milling the materials together for a number of hours.

The nylon-coated rubber thread upon leaving the receptacle I8 passes downwardly, while maintained at constant elongation, through a drying chamber, such for example as a glass tube 24 which may be heated to the desired temperature by the electrically heated wire coil 25 having th electrical connection shown, and this coil may be maintained at the desired temperature by employing the variable resistance 26. The tube 24 which may conveniently be approximately two feet long is maintained at a temperature somewhere around 200 F., depending somewhat upon the rate at which the thread I0 passes therethrough, so that most of the solvent will be evaporated within this heated tube. The

coated thread then passes downwardly within a tank 21 containing a volatile hardening liquid such as an acetone bath 28, and the coated thread passes around a grooved roller 29 mounted in this tank and which is preferably driven at a predetermined speed by a gear 30 secured to the supporting shaft for this roller. The wetted strand then passes upwardly for a substantial distance through the air to give its coated surface a chance to dry, and at the up per end of its travel it passes around a grooved roller 3I having a supporting shaft to which is secured the driving gear 32, so that this roller 3| may be driven at the same speed or a slightly higher speed than the grooved roller 29.

The rubber thread with a continuous nylon coating thereupon, upon leaving the grooved roller 3|, should be sufliciently dry and hard to enable the elastic yarn to be wound up on the take-up reel 33 having the supporting shaft 34 that slides up and down within notches provided at the uppzr ends of the upright posts 35. The yarn is guided to this reel by the traverse bar 33, and the yarn on this reel engages the reel supporting and driving roller 31 having a supporting shaft to which is secured the driving gear 38.

The driving gears I6, 30, 32 and 38 all should be positively driven at definite ratios to each other, and by properly determining these ratios the desired degree of constant elongation may be maintained in the rubber thread during the thread covering operation. The surface speed at which the let-off spool I2 is rotated will of course be considerably lower than the surface speed of the other thread-advancing means described.

The finished elastic yarn of the present invention should be capable of being stretched elastically at least 50% and in many construction an extensibility of over is desired. The nylon cover Il may be dyed various colors and it provides a smooth tough and durable outer surface which is pleasin in appearance and is capable of givin the elastic yarn a long durable life. When embodied in a knitted fabric it will not run or ladder nearly as readil as will ordinary knitted goods. A knitted garment made of this elastic yarn can be readily set to the shape of a form by dipping the form and knitted goods in warm or hot water and then drying.

In some constructions it is found that after the elastic yarn of the present invention has been stretched a substantial amount and then allowed to retract, the nylon coating will show" minute annular wrinkles due to the failure of the coating to retract to quite the same extent as the core, but this is not an objectionable feature.

The nylon herein contemplated is a linear polyamide having a molecular weight of at least 5,000. The selection of such a nylon for use in the present invention and having the requirements herein set forth will be obvious to those skilled in the nylon art.

The film-forming linear polyamides are characterized by relatively high melting points, far above 212 F., so that the elastic yarn will not be injured by hot water. The thickness of the nylon coat may be controlled by controlling the size of the tube 23 relatively to that of the thread I0 passing therethrough, and by the number of passes through the coating bath. After this elastic yarn has been woven or knitted intoa fabric the stretch characteristics of such fabric may'be increased by boarding the fabric or holding it stretched in hot water at 70 to 80 C. In order to disclose the present invention further the following tables are given.

TABLE I Physical properties of nylon-coated elastic yarn having a round rubber core .0135" in diameter 1. Composition (by weight)--- 60 to 65% rubber and 35 to 40% nylon 2. Yards per pound (approx.) 12,000

3. Length of rubber in one yard of (relaxed) elastic yarnto 11" g 4. Elongation of rubber in relaxed elastic yarn 225 to 250% 5. Strength of elastic yarn at break 6 Breaking elongation of elastic yarn 250 to 300% 7. Gauge of relaxed elastic yarn .0075":.001"

TABLE 11 Physical properties of nylon-coated elastic yarn having a round rubber core .01" in diameter The reason the gauge of the elastic yarn, item '7 of each table, is smaller than the uncoated 4 round core is that the heading or each table gives the diameter of the core when relaxed or unstretched, while in the finished elastic yarn the core is held stretched over 200% in Table I and over 300% in Table II which reduces its diameter.

The elastic yarn of the present invention is stronger than ordinary elastic yarn having a textile cover wound upon a rubber core when compared on a yards per pound basis, and this new elastic yarn can be produced at high speed and at low cost.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. An elastic yarn fine enough to be knitted and woven to form light weight elastic fabrics, comprising a stretchable rubber core that is completely surrounded by a thin continuous jacket formed of a tough stretchable film of nylon deposited as a coating on the rubber core so as to hold the core partly stretched when the elastic yarn is relaxed, and adapted to contract and stretch readily with said core to more than twice the length of the relaxed elastic yarn.

2. An elastic yarn fine enough to be knitted and woven to form light weight elastic fabrics, comprising a stretchable rubber core that is completely surrounded by a thin continuous jacket formed of a tough stretchable film of nylon deposited as a coating on the rubber core so as to hold the core partly stretched when the elastic yarn is relaxed, and adapted to stretch fifty percent or more with the core in the elastic yarn.

3. An elastic yarn fine enough to be knitted and woven to form light weight elastic fabrics, comprising a stretchable rubber core that is completely surrounded by a thin continuous jacket formed of a tough stretchable film of nylon deposited as a coating on the rubber core so as to hold the core partly stretched when the elastic yarn is relaxed, the weight of the core being greater than that of the coating, and the coating being adapted to contract and stretch with the core to more than twice the length of the relaxed elastic yarn.

BOUTWELL H. FOSTER.

REFERENCES CITED The following references are of record in the die of this patent:

UNITED STATES PATENTS Number Name Date 2,155,621 Shepherd Apr. 25, 1939 2,297,585 Shepherd Sept. 29, 1942 2,392,842 Doell Jan. 15, 1946 2,393,006 Vincent Jan. 15, 1946 2,401,291 Smith May 28, 1946 2,417,453 Wade Mar. 18, 1947 2,442,279 Alderter May 25, 1948 

1. AN ELASTIC YARN FINE ENOUGH TO BE KNITTED AND WOVEN TO FORM LIGHT WEIGHT ELASTIC FARBICS, COMPRISING A STRETCHABLE RUBBER CORE THAT IS COMPLETELY SURROUNDED BY A THIN CONTINUOUS JACKET FORMED OF A TOUGH STRETCHABLE FILM OF NYLON DEPOSITED AS A COATING ON THE RUBBER CORE SO AS TO HOLD THE CORE PARTLY SRETCHED WHEN THE ELASTIC YARN IS RELAXED, AND ADAPTED TO CONTRACT AND STRETCH READILY WITH SAID CORE TO MORE THAN TWICE THE LENGTH OF THE RELAXED ELASTIC YARN. 